1. Field of the Invention
This invention relates to a modified polyolefin useful as a modifier for engineering plastics and the like. More particularly, this invention relates to a modified polyolefin useful as modifier for engineering plastics such as polyesters, polyamides, etc., and as an adhesion improver for improving adhesion of such engineering plastics with fillers to be compounded therein.
1. Description of Related Art
Polyolefins are used widely in various applications as films, fibers, molded articles, etc. since they are produced industrially at low cost and are superior in molding properties, insulating properties, resistance to chemicals, mechanical strength, etc.
Recently, studies have been made extensively to melt and mix two or more polymers having different properties to obtain resin compositions having the respective features of the polymers. There have been developed many resin compositions having compounded therein polyolefins in order to make most of their characteristics.
However, resin compositions having compounded therein polyolefins themselves suffer poor compatibility because of the polyolefins being non-polar. More particularly, the polyolefins do not disperse uniformly when they are kneaded simply and conversely their rigidity, impact strength, elasticity, etc. decrease so that no resin compositions can be obtained that have desired physical properties.
In order to improve the compatibility of polyolefins, it has conventionally been known to modify polyolefins or blends of polyolefin and rubber or the like with maleic anhydride, unsaturated epoxy compounds or the like (Japanese Patent Application Laid-open Nos. 52156/1975, 105993/1977, 50040/1980, 67743/1983, 236214/1988, etc.).
However, such modified polyolefins or modified polyolefin elastomers have some disadvantages. That is, upon their preparation reaction, a decomposition reaction of the polyolefin main chain proceeds simultaneously so that there can be obtained only low molecular weight modified products. In addition, maleic anhydride and other substances used for modification are sublimating monomers which have irritating odors, and hence their working efficiencies upon melting reaction are not so high. Furthermore, the modified polyolefin and modified polyolefin elastomers thus obtained are not always sufficient as a compatible plasticizer since it is difficult to increase the graft ratio of maleic anhydride or the like therein to high enough a level.
Recently, modified polyolefins and modified polyolefin elastomers have been proposed in which glycidyl esters of acrylic acid or methacrylic acid are used as a modifier.
Also, there have been proposed resin compositions composed of polyamides, polyesters or the like blended with polyolefins or polyolefin elastomers modified with unsaturated glycidyl compounds represented by general formula (I) below ##STR2## wherein R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; Ar is an aromatic hydrocarbon group having 6 to 20 carbon atoms and having at least one glycidyl group; and n is an integer of 1 to 4 (WO91/14717, Japanese Patent Application Laid-open Nos. 23814/1992, 43764/1993, 86276/1993, etc.)
Here, glycidyl acrylate (GA), glycidyl methacrylate (GMA) and the compound of general formula (I) above used as a modifier have high reactivity and high reaction efficiency, and hence these modifiers give high graft ratio upon modification and the resin compositions obtained by melt-mixing the resulting modified polyolefin with the various engineering plastics described above have good dispersion compatibility and excellent physical properties.
However, these modifiers are highly homopolymerizable so that in the graft reaction upon the modification, they do not disperse in the polyolefin as monomer units but graft on the polyolefin as a polymer. As a result, reaction sites concentrate on certain points on the polymer, and the modified polyolefin as a whole has decreased reactivity and reaction efficiency.
Therefore, an object of this invention is to increase dispersability of the aforementioned modifier monomer in polyolefins and provide a modified polyolefin having improved reactivity and reaction efficiency.
As a result of intensive investigation, it has now been found that modification of polyolefins with the aforementioned reactive monomer and other monomer which is highly compatible therewith in combination enables good dispersion of the reactive monomer in the polyolefin, and gives rise to modified polyolefins which are superior in reactivity and reaction efficiency to the polyolefins modified with the aforementioned reactive monomer alone. This invention has been completed based on this discovery.